The present invention generally relates to an apparatus for finishing a conic surface and, in particular, relates to one such apparatus having rigid members defining planes that, intersect in a line collinear with the axis of the conic surface.
It is known that conventional surfaces requiring near normal incident angles are quite inefficient for optical purposes when the incident radiation of interest is in the ultraviolet or X-ray regions of the electromagnetic spectrum. This inefficiency is attributed to the poor reflectivity of conventional surfaces at these spectral regions. Consequently, when operating in the ultraviolet or X-ray region grazing incidence optical systems are employed.
One particularly efficient surface commonly used for grazing incidence optical systems is a conic surface having a longitudinal axis. One major difficulty of fabricating such a surface is the efficient grinding and polishing, i.e., finishing, thereof. Conventionally, a typical finishing tool is a substantially rigid rectangular block of material having a contact face that is curved to approximate the shape of the conic surface.
Such a tool, however, is quite inefficient because a conic surface has both a longitudinally changing radius of curvature and a transversely changing radius of curvature. Such compound changes of radii of curvature prevent the efficient rotation of such a tool against the optical surface during finishing. Further, if such a tool is moved longitudinally, or parallel, to the optical axis, the change of radius of curvature causes a misfit between the tool and the surface being finished.
One approach to resolving this problem has been to finish such an optic using a long but very narrow tool. While such a scheme does maintain a better fit of the tool to the surface, the tool must be quite narrow. The use of a narrow tool generally greatly increases the time needed for finishing a grazing incident optic since the material removal of a finishing tool is dependent on the surface contact area between the tool and the surface. Further, with a long narrow tool the changing longitudinal diameter of the optic restricts the maximum excursion of the tool. This restriction further reduces the material removal rate.
Consequently, there is a substantial need and desire for an apparatus for finishing a conic surface that enables both full rotational finishing and extended excursion finishing.